This fascinating map is taken from the Journal of the Manchester Geographical Society which published an address given by William Sherratt on April 4th 1888.
Here are a few snippets as regards the reservoirs of the Longdendale Valley.
Longdendale was chosen as a source due its purity taking only second place within the UK to that at Loch Katrine. There is a softness in the Manchester water and a freedom from those salts and chemicals held in solution which give to other water supplies their varying hardness.
The Longdendale gathering grounds will be seen on the map, where the valley into which the water flows and river Etherow are shown. It was damned up and made into reservoirs. The area of this drainage ground is 19,300 acres of thirty square miles. There are 975 acres of water.
The height of Woodhead above the Ordnance level is 782ft. The water is sent on from Rhodes Wood reservoir to Arnfield and Hollingworth by its own gravitation.
There are innumerable springs. Each spring, as it is found, is tapped and the flow conducted into what is called a spring-water conduit. There is an arrangement by which this conduit simply takes up the pure spring water and lets the flood water go into Woodhead reservoir. There is a weir which receives the water from Heyden Brook. This pure spring-water conduit goes underneath. The moment any rain or flood comes it swells the stream at once, and instead of the water falling into the pure spring-water conduit it escapes over the sill.
At Hollingworth there are houses for the incubation of fish. Char and trout are turned into the reservoir and their presence does away the fishy odour and taste which arose from a species of snail. The fish act as scavengers.
To read the whole text view this pdf file.
Godley reservoir lies on the Manchester side of the Longdendale reservoirs. See a track to Godley reservoir on Hyde Daily Photo.